1. Field of the Invention
The present invention relates to a structure and method for firmly and electrically welding an electrically conductive connecting member, such as a sheathed conductor having a small diameter, a flexible printed wiring board or the like, to an electrically conductive metallic member, such as a terminal, a busbar or the like, by using a laser light beam.
2. Background
FIG. 17 is a perspective view of a conventional structure employable for welding electrical connecting portions to each other using a laser light beam.
This conventional structure is designed such that a conductor portion (consisting of a bundle of lead wires) 82 of a sheathed cable 81 is placed on the surface of an electrically conductive metallic plate 80 such as a terminal, a busbar or the like and a laser beam 83 is irradiated on the conductor portion from above so as to weld the conductor portion 82 to the electrically conductive metallic plate 80. Referring to FIG. 18, when a polyurethane sheathed conductor 86, having a small diameter, is connected to an electrically conductive metallic plate 88, a laser light beam 87 is irradiated directly on the sheathed conductor 86 Without the sheath 91 peeled away therefrom.
With the conventional structures mentioned above, there arises a problem in that the welded portion 84, 89 of the cable 81, 86 is largely recessed as illustrated by reference numeral 85, 90, causing the tensile strength of cable 81, 86 to be remarkably reduced. Moreover, in the case where the sheathed conductor 86 is welded directly to the electrically conductive metallic plate 88 as shown in FIG. 18, vapor resulting from vaporization of the sheath part 89 generates a number of voids, or bubbles, 92 which in turn cause a substantial reduction of the strength of the welded structure.